The head of the Transportation Security Administration has backed off
a public commitment to conduct a new independent study of X-ray body scanners
used at airport security lanes around the country.

Earlier this month, a ProPublica/PBS NewsHour investigation found that
the TSA had glossed
over research that the X-ray scanners could lead to a small number
of cancer cases. The scanners emit low levels of ionizing radiation, which
has been shown to damage DNA. In addition, several safety reviewers who
initially advised the government on the scanners said they had concerns
about the machines being used, as they are today, on millions of airline
passengers.

At a Senate hearing after the story ran, TSA Administrator John Pistole
agreed to a request by Sen. Susan Collins, R-Maine, to conduct
a new independent study of the health effects of the X-ray scanners,
also known as backscatters.

But at a Senate
hearing of a different committee last week, Pistole said he had since
received a draft report on the machines by the Department of Homeland Security’s
inspector general, or IG, that might render the independent study unnecessary.

“My strong belief is those types of machines are still completely safe,”
Pistole said. “If the determination is that this IG study is not sufficient,
then I will look at still yet another additional study.”

According to a summary obtained by ProPublica, the inspector general
concluded the machines are within industry standards for radiation exposure
limits. But the summary also suggests the report focuses mostly on how
the TSA monitors and maintains the machines. The full report won’t be released
for several weeks.

“I hope the Obama administration is not backing away from an independent
study of the health effects of these radiation-emitting machines,” Collins
said in a statement to ProPublica. “What I asked for — and what the administrator
committed to — was an independent study on the health effects of [the]
machines, not just a study on whether TSA is doing an adequate job of inspecting,
maintaining and operating” them.

The inspector general’s report calls on the TSA to ensure that radiation
surveys are conducted for unintended emissions, that calibrations are consistently
documented and that airport screeners complete annual radiation safety
training. The inspector general also advised the agency to determine how
much on-the-job training is needed for screeners who operate the backscatters
and to ensure that accidental radiation overdoses are properly reported.

It’s unclear whether the recommendations resulted from any problems
found during the investigation, or are general reminders about best practices.
It’s also unclear whether investigators measured the radiation doses from
the machines themselves or relied on inspections conducted by the manufacturer.

The
TSA uses two types of body scanners. With the backscatter machines
that have been the focus of health concerns, a passenger stands between
two large blue boxes and is scanned with a pencil X-ray beam that moves
rapidly left to right and up and down the body. With the other kind of
scanner, called a millimeter-wave machine, a passenger enters a chamber
that looks like a round phone booth and is scanned with a form of low-energy
radio waves, which do not strip electrons from atoms and have not been
shown to cause cancer.

In recent years, the TSA has commissioned tests of the X-ray scanners
by the Food and Drug Administration and the Johns Hopkins University Applied
Physics Laboratory. In addition, survey teams from the Army Public Health
Command visit airports to check the machines.

Those tests have all shown that the X-ray scanners emit extremely low
levels of radiation, equivalent to the radiation received in a few minutes
of flying. But the tests haven’t doused questions from some outside radiation
experts about why the TSA doesn’t use only the millimeter-wave machines,
which the agency also deems highly effective.

But others have pointed to problems with millimeter-wave machines. Germany
announced earlier this year that it would forgo the machines after concluding
that they produced too many false positives.

There are currently 500 body scanners, split about evenly between the
two technologies, deployed in airports. The TSA plans to deploy 1,275 backscatter
and millimeter-wave scanners covering more than half its security lanes
by the end of 2012 and 1,800 covering nearly all lanes by 2014.